The present invention relates to a numerical control unit, and more particularly to a numerial control unit which adopts a packaging method capable of readily dealing with an increase in the number of axes to be controlled.
A standard numerical control unit which performs data processing through the operating function of a processor controls four to five axes at most; this number is sufficient for general use but, in some cases, there is needed a numerical control unit capable of controlling ten-odd axes for some special purposes. A method that is usually considered for constituting the numerical control unit for such many-axis control is to directly connect circuits other than axis-control circuits, such as a tape reader, an NC control panel, etc., to a main bus of a main processor and to connect a required number of axis-control circuits to the main bus. With such an arrangement, however, as the number of parts connected to the main bus is markedly larger than in the case of the standard numerical control unit, the electrical load on the main processor increases and the main bus becomes huge, resulting in such inconvenience that standard circuit parts prepared for the standard numerical control unit, such as a mother board, a storage cabinet and forth, cannot be used. In general, it is advantageous in terms of manufacturing costs and stock control to standardize as many parts as possible; therefore, it is desirable that the numerical control unit for many-axis control could also be constituted using such standard parts. Further, in order for the unit to have a high degree of flexibility, it is also desired that the unit has a construction that allows ease in increasing the number of axes to be controlled.